The present invention relates to information display systems for aircraft guidance and more particularly to such a system for presenting sufficient information to a helicopter pilot to enable him to check the area for obstacles and to hover over a selected ground location.
At the present time a pilot, during the day and if the day is clear, can visually recognize objects on the ground or land features. He may then maneuver his helicopter and hover over a target object or feature by visually aligning his helicopter with other ground features and watching his altimeter. The accuracy of his hovering maneuver depends on his own skill and the availability of visible terrain features. A skilled helicopter pilot can, for example, hover and descend directly over an injured person who is to be evacuated and can maintain a hover position within 15 feet of a selected ground feature.
The presence of fog, smoke or nighttime operation presents an entirely different problem to a pilot who wishes to locate a certain ground position and accurately hover over that position. The problem is less serious if the area is lighted, for example, by flares or spotlights, or if the night is illuminated by bright moonlight or if the helicopter is equipped with a spotlight and the pilot is able to use it. However, there are occasions, particularly in military combat situations, where lights cannot be used without revealing the presence, to the enemy, of the helicopter (in the case of a helicopter spotlight or flare) or the presence of ground personnel (in the case of ground lighting). Such nighttime and hidden operations may be required, for example, to evacuate a pilot shot down behind enemy lines, to supply an isolated outpost in the possible presence of enemy troops, or to attack enemy tanks or other enemy forces under cover of darkness.
It is an objective of the present invention to provide an information display system for use by a helicopter pilot which would enable the pilot to hover his helicopter over any ground position selected by him.
It is an objective of the present invention to provide an information display system for use by a helicopter pilot which will provide sufficient information so that, without excessive training time or unusual pilot skill, he may hover within a few feet of his selected ground object or feature.
It is an objective of the present invention to provide such an information display system for use by a helicopter pilot which will permit him to hover over a target even in the fog or at night without artificial illumination of the target or its area and without the presence of moonlight.
It is an objective of the present invention to provide an information display system for use by a helicopter pilot which will present on a screen simultaneously information about the area forward of the helicopter and information about the area underneath the helicopter; and both sets of information will be in their usual vertical order, with the forward area presented above the ground area, for ready comprehension.
It is an objective of the present invention to provide an information display system for use by a helicopter pilot which will show, using a representative symbol on a screen, the position of the aircraft in relationship to the features or objects on the ground.
It is an objective of the present invention to provide an information display system for use by a helicopter pilot which will show, using representative symbols on a screen, the altitude of the helicopter and the rate (velocity) of its ascent or descent.
It is an objective of the present invention to provide an information display system for use by a helicopter pilot which will show, using representative symbols on a screen, the velocity or movement of the aircraft relative to a selected ground object and its acceleration relative to such object.
It is a feature of the present invention to provide a system for displaying information to a pilot to enable him to hover his helicopter over a selected location. The system includes an image camera, such as a forward-looking infrared sensor or television camera or the like, having an effective viewing angle and mounted on the helicopter so that said viewing angle is substantially forward looking. Hereinafter the term "image camera" will include any device which can generate a picture of an area. A mirror is positionable so that it may be located within the viewing angle to thereby reflect ground information to the camera when the helicopter is hovering. The system also includes means to stabilize the mirror against the pitch and roll of said helicopter, a television monitor mounted within the helicopter, and means to transmit and invert the image from the image camera to the television monitor. Consequently, the image reflected from the stabilized mirror will appear in the bottom portion of the monitor screen.
In one embodiment of the present invention the means to stabilize the mirror includes a gimbal mounting fixed to the helicopter and a bracket fixed to the mirror, a first and a second shaft perpendicular to each other, a first motor and a second motor to respectively position the first shaft and the bracket, two motor control means each to control each of said motors, and a pitch and roll gyroscope connected to provide position signal information to respective ones of said motor control means.
It is a further feature of the present invention to provide, in the system, a pair of position sensing transducers and a pair of electronic amplifiers, those transducers and amplifiers being connected to provide shaft position feedback to the respective motor control means.
It is a further feature of the present invention to provide, on the lower portion of the monitor viewing screen, means to symbolically represent and display the position and rate of direction of movement of the helicopter.
The lower portion of the viewing screen preferably also shows means to symbolically represent and display the acceleration and direction of acceleration of the helicopter and means to symbolically represent and display the altitude and rate of ascent or descent of the helicopter.